Environmental Issues - Class 12 Medical Biology - Extra Questions

$$\textbf{Solution: }$$ 

$$\bullet$$The gradual accumulation of the non degradable substances in the species such as pesticides is termed as bioaccumulation. 

$$\bullet$$The accumulation of the toxins in the food chain along the increasing trophic level of the food chain is defined as biomagnification. 

$$\bullet$$DDT and mercury are moderately toxic which is the main component causing biomagnification.

Delhi is the fourth most polluted city in the world in a list of 41 cities. The burning of fossil fuels like petrol and diesel has added to the pollution of air in Delhi. So, in the year 2002 it switched over to a new fuel - CNG (compressed natural gas). It is considered better because CNG is a clean fuel that produces very little unburnt particles and thus it is considered as eco-friendly. CNG burns most efficiently, unlike petrol or diesel, in the automobiles and very little of it is left unburnt. Moreover, CNG is cheaper than petrol or diesel, cannot be siphoned off by thieves and adulterated like petrol or diesel.

1. The unleaded petrol does not have the lead compound which produces harmful gases, So it does not emit harmful gases into the environment.
   
2. As unleaded petrol does not emit harmful compounds, it helps in preventing health diseases like bronchitis, asthma, lung diseases and other respiratory disorders. 
   

• Greenhouse gases (CFCs, methane, carbon dioxide etc.) in the atmosphere acts like a mirror and reflect back the heat radiations. This prevents the escaping of heat from the earth's atmosphere such phenomena is known as the greenhouse effect and cause of the rise in the atmospheric temperature, which is known as global warming. 

When the sunlight reflects back from earth's surface some of the heat get trapped by the gasses like carbon dioxide, nitrous oxide etc., and increases the temperature of the environment such effect is called as the greenhouse effect.

Measures to control greenhouse effect:

(i) Disposing of the greenhouse gasses as they are formed elsewhere than in the atmosphere.

(ii)Prevention of deforestation and planting of more trees.

$$\textbf{Solution:}$$

(i)

$$\bullet$$ Rahul's father choice of purchasing gift is better them him because a plant sapling will convert into a tree after some months if it is grown and taken care properly. When the sapling grows and develops, it provides oxygen and other benefits to human.

$$\bullet$$ But wooden toy is prepared from wood obtained from the trunk of a cut tree. A wooden toy is one of the factors causing deforestation. Thus, it is not a better gift.

(ii)

$$\bullet$$ Other eco-friendly gifts can be products working with solar energy like a solar cooker, or any pet like a puppy, kitten, etc.

$$\textbf{Solution:}$$

$$\bullet$$ Deforestation destroys the natural habitat of animals and hence, affects the wildlife.

$$\bullet$$ Forests are the natural habitats of animals. Reduction in the forest area due to cutting down of trees for human activities and purposes results in the destruction of natural habitats of most of the animals.

$$\bullet$$ Trees present in forests are the home for many birds, reptiles, and other animals. Destruction of trees affects the population of animals that stay on trees.

• Algal blooms can be defined as the  rapid increase or accumulation of algae in the water bodies which can be recognised by the discoloration in the water.
• It is mainly cused due to excess of nutrients such as phosphorus and nitrogen in the water and also increasing temperature.
• Algal blooms decrease the oxygen level in water thus, making it difficult for aquatic animals to survive.
  

Explanation: 

• E-waste is the electronic waste that is produced by all the items used in electronic equipment or the electronic industry.

• They are harmful chemicals that are really harmful to humans as well as the environment.

• E-waste is generated because of the usage of polluting substances like plastics,  lead, cadmium, and mercury.

• These are non-biodegradable substances.

• They are very dangerous and polluting.

• They also have been found to cause several life-threatening diseases, including cancer.

• As displayed in the figure there is a sharp decline in the amount of oxygen concentration at the summit of sewage water and natural water.
  
• While as the flow of water moves the number of oxygen increases slowly.
• The increased amount of oxygen leads to the death of zooplankton and phytoplankton species.

• Global warming is the increase in the temperature of earth due to increase in the greenhouse gases such as carbon dioxide, methane, CFCs etc which absorb some of the radiation from the sun that is supposed to be re-emitted back in the space. This increases the temperature of the earth surface.
• There are many causes of increasing global warming major one is deforestation, others are such as an increase in the emission of gases from industries, vehicles, increasing population etc.

1. Reforestation is the first step to be taken in the direction to decrease global warming. Increase in the number of trees will help to increase absorption of Carbon dioxide which will decrease the amount of gas in the atmosphere.
2. a release of CFCs is also the main cause in increasing global warming. Therefore a decrease in the production of CFC will help as CFC has a major role in the destruction of the ozone layer. When Cl released from the CFC reaches the ozone layer the Cl ion reacts with the Oxygen of the ozone and release oxygen, one molecule of Cl will remain in the stratosphere and degrade the ozone layer for a long time before it degraded itself.
3. Cutting down the use of fossil fuel and opting for the use of renewable energy resources such as hydropower, wind energy, etc
4. Try to decrease the rate of human population growth as the resources present on earth are limited and consumers are increasing constantly which means the release of more greenhouse gas and an increase in global warming. Therefore the population increase should be controlled.
   

• E waste also known as electronic waste include used up devices such as tabs, laptops, televisions and all other home appliances.
  
• Electronic waste contain materials such as lead, cadmium or beryllium which on disposable involve significant risk to health of workers and the environment.
• Improper disposal of e-waste affects the soil, air and water components of the environment.
  
• These chemicals lead the death of the plants and animals living in water. Some chemicals are carcinogenic, which can cause cancer. 
• Sometime intake of contaminated water by humans and animals cause lead poisoning. 
  

• Biomagnification stands for Biological Magnification, which means the increase of contaminated substances or toxic chemicals that take place in the food chains. These substances often arise from intoxicated or contaminated environments. The contaminants include heavy metals namely mercury, arsenic, pesticides such as DDT, and polychlorinated biphenyls (PCBs) compounds which are then taken up by organisms because of the food they consume. The harmful substances then build up inside the organism’s cells. When organisms in the higher food chain consume the organisms containing the toxins below their trophic levels, the toxins gradually become concentrated in the higher food chain. Because this is a repetitive process in the ecosystem and throughout the entire food chain, the higher organisms are the ones that will accumulate most of the toxins. Agricultural pesticides, fungicides, herbicides, and chemical fertilizers, among other agricultural chemicals, are highly toxic and often find the way into the soils, rivers or lakes and the seas through surface stormwater runoff. It disrupts the interconnected relationships within the food chain. An example of biological magnification and its dangers is any small fish that eats plankton that has been tainted with mercury.
  
• Bioaccumulation is the accumulation of substances, such as pesticides, or other chemicals in an organism. Bioaccumulation occurs when an organism absorbs a substance at a rate faster than that at which the substance is lost by catabolism and excretion. An example of bioaccumulation is the use of DDT as an insecticide in the 1950s and 1960s. Birds of prey were badly affected because it made the shells of their eggs very thin, causing them to break easily when the birds tried to incubate them.
  

• Environmental protection is the practice of protecting the natural environment and its resources by individuals, organizations and governments.
•  The objectives of various environmental protection laws are to conserve natural resources and the existing natural environment.
•  It also aims to repair damage and reserve trends, wherever possible.

• Electrode wires produce a corona that releases electrons.
• These electrons attach to dust particles and give them a net negative charge.
• Grounded collecting plates attract negatively charged dust particles.
• Thus dust particles are removed from air.
• A spray of water or lime is generated in the scrubber and exhaust is passed through this spray. Scrubber removes gases; like Sulphur dioxide from air.
• Thus polluting gases; like Sulphur dioxide are removed from air.

The amount of dissolved oxygen needed (i.e. demanded) by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period. During the secondary treatment of primary effluents, the BOD level decreases because useful microbes consume a major part of the organic matter. Reduction in the organic matter leads to lowering of BOD.

• Biochemical oxygen demand or biological oxygen demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms to break down organic materials present in a given water sample at certain temperature over a specific time period. When BOD levels are high, dissolved oxygen levels decrease because the oxygen that is available in the water is consumed by the bacteria. Hence, the higher the BOD higher the water is polluted.
  
• The BOD value of sample A is 20 mg/L, which is the secondary effluent discharged from a sewage treatment plant.
• The BOD value of sample B is 8 mg/L, which is the river water and it is least polluted.
• The BOD value of sample C is 400 mg/L, which is untreated sewage water and it is highly polluted water.

• In summer the temperature of the water bodies rises with increase in temperature of the surroundings.
• As a result of increase in temperature, the solubility of gases in the water bodies decreases.
• Therefore, less amount of dissolved oxygen is available for aquatic animals.

Ozone is found at the higher levels of the earth’s atmosphere, and it is identified as a deadly poisonous gas because it can cause various respiratory problems.

The chemical formula for ozone is $$ \left (O_{3}  \right )$$ . The concentration of ozone molecules is higher in the stratosphere layer of the earth’s atmosphere. The formation of ozone molecule in the earth’s atmosphere mainly occurs from two-step reactive procedure. The first step includes the splitting of an oxygen molecule $$ \left (O_{2}  \right ) $$ in the presence of sunlight into two oxygen atoms. The two oxygen atoms further collide with another oxygen atom present in the atmosphere to form ozone $$ \left (O_{3}  \right ) $$.

The equation for the formation of ozone in the earth’s stratosphere is as follow:

$$ O_{2}\xrightarrow[]{Sunlight}2O $$

$$ O+O_{2}\xrightarrow[]{ }O_{3} $$

Any damage to the ozone layer can cause a serious concern because ozone layer acts as a protecting covering that shields the earth’s surface from harmful ultraviolet radiation. The ultraviolet emissions produced by the sun are highly damaging to the living organism, and it also results in causing skin cancer and other severe disorders in human beings. Thus, damage to the ozone layer is a cause of concern as the harmful radiations produced by the sun now can enter into the earth’s atmosphere.

The following three human activities (anthropogenic activities) can increase carbon dioxide in the atmosphere:

1. Burning of fossil fuel, like coal, for generation of electricity or for factories purpose emit large quantities of CO$$_{2}$$.

2. Fumes from the vehicles contribute to the increase in the CO$$_{2}$$ levels

3. Deforestation to acquire land for agriculture and urbanization leads to increase in CO$$_{2}$$ levels as plants absorb that gas.

$$\textbf{Solution: }$$ 

$$\textbf{Factors determining amount of Dissolved Oxygen in water include the following: }$$

$$\textbf{Water temperature:}$$

$$\bullet$$The cold water has the possibility to hold more dissolved oxygen as compared to the warm water. 

$$\textbf{Presence of organic water:}$$

$$\bullet$$Biochemical Oxygen Demand (BOD) is the amount of oxygen required by the microorganisms in milligrams in 5 days to completely decompose the organic wastes present in one litre of polluted water at 20°C. 

$$\bullet$$BOD shows an inverse relationship with the dissolved oxygen (DO). 

$$\bullet$$Higher is the amount of oxygen required, the greater is the degree of organic pollutants. 

 $$\textbf{ Salinity:}$$

$$\bullet$$Salty water holds less oxygen than fresh water. 

$$\textbf{ Vegetation:}$$

$$\bullet$$The presence of vegetation in the water body can elevates the water oxygen content while performing the process of photosynthesis. 

$$\bullet$$Vegetation shading a stream may decrease water temperatures which indirectly increases the amount of dissolved oxygen. 

$$\bullet$$Harmful effects of nitrate, fluoride and arsenic salts in ground water on humans:

$$\bullet$$Ill effects of nitrates: 

$$\bullet$$Cyanosis (Blue baby syndrome) is the disease associated with the accumulation of nitrates in the human body. 

$$\bullet$$The contamination of the nitrates by the water supplied to the child's body converts into nitrites which bind to the hemoglobin in the body, forming methemoglobin. 

$$\bullet$$The compound methemoglobin is unable to carry oxygen.

$$\bullet$$Ill effects of fluorides:

$$\bullet$$Excess of fluorides in drinking water can result in fluorosis and can affect the bones and teeth of the human body.  

$$\bullet$$Ill effects of Arsenic:

$$\bullet$$Blackfoot disease is a  vascular disease which is caused due to the excess amount of exposure to arsenic. 

$$\bullet$$Arsenic is circulated in the region through drinking water. 

$$\bullet$$This damages the vascular system of the human body affecting its lower limbs and severely damaging it.  

• Ozone is the inorganic molecule and is an unstable molecule of oxygen. Its composition is C$$_3$$ also called as trioxygen. They are formed in the outer layer of the atmosphere with the help of the reaction of free oxygen with an oxygen molecule. 
• Their main function is to protect the earth from the rays of the sun as well as from the ultraviolet radiation. They are also helpful in lowering atmospheric temperature and thus results in the decrease of global warming.
• Due to the increased use of refrigerators and air conditioners, the release of chlorofluorocarbons (CFCs) is increased. This CFC gas when goes into the atmosphere breaks and releases one chlorine atom. This chlorine atom is responsible for the destruction of the ozone layer. The continuous depletion of ozone has raised a hole known as the ozone hole and this process is called called ozone depletion.

1.  Some of the electronic wastes may contain valuable metals such as gold and copper - The statement is true.
2.   Flyash is the gaseous waste of cement industry - The statement is true
3. The statement is false. Electricity is not one of the primary needs but the secondary needs of human society.